学步园

在C# 2.0中提供了Generic支持，我们的Factory就也应该支持Generic，以下是我在LiteMDA的BusinessObjectFactory中的实现，同时支持Generic和非Generic的类。

关于Interface及其对应的Assembly和Class的描述信息存在以下的BusinessObjectConfiguration.config中：

<?xml version="1.0" encoding="utf-8"?>
<BusinessObjectConfiguration>
  <xmlSerializerSection type="LiteMDA.Configuration.BusinessObjectConfiguration, LiteMDA.Configuration, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null">
    <BusinessObjectConfiguration xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
      <VisibleBusinessObjects>
        <BusinessObject>
          <InterfaceName>LiteMDA.BusinessObjectFactory.Test.ITestClass</InterfaceName>
          <Class AssemblyName="LiteMDA.BusinessObjectFactory.Test.exe" ClassName="LiteMDA.BusinessObjectFactory.Test.TestClass" />
        </BusinessObject>
        <BusinessObject>
          <InterfaceName>LiteMDA.BusinessObjectFactory.Test.IGenericTestClass`2[System.String,System.Object]</InterfaceName>
          <Class AssemblyName="LiteMDA.BusinessObjectFactory.Test.exe" ClassName="LiteMDA.BusinessObjectFactory.Test.GenericTestClass`2[System.String,System.Object]" />
        </BusinessObject>
        <BusinessObject>
          <InterfaceName>LiteMDA.BusinessObjectFactory.Test.ITestClass2</InterfaceName>
          <Class AssemblyName="LiteMDA.BusinessObjectFactory.Test.exe" ClassName="LiteMDA.BusinessObjectFactory.Test.GenericTestClass`2[System.String,System.Object]" />
        </BusinessObject>
      </VisibleBusinessObjects>
    </BusinessObjectConfiguration>
  </xmlSerializerSection>
</BusinessObjectConfiguration>

以上的Configuration中定义了三个可以被BusinessObjectFactory构造的类，构造时只需提供Interface，这里给出了三种典型的情况，一个是非Generic、一个是接口为Generic，类也为Generic，第三个是接口非Generic，类Generic。

BusinessObjectFactory的源码如下：

using System;
using System.Collections.Generic;
using System.Text;
using System.Reflection;
using LiteMDA.Configuration;
using Microsoft.Practices.EnterpriseLibrary.Configuration;

namespace LiteMDA.BusinessObjectFactory
{
    /**//// <summary>
    /// ObjectFactory is the only gateway for creating Business Objects.
    /// </summary>
    public sealed class ObjectFactory
    {
        private ObjectFactory()
        {
        }

        /**//// <summary>
        /// _ObjectMap saves all the BOI/BO mapping pairs, this field will 
        /// be constructed from the BOI exposing configuration file at the 
        /// first time when the CreateObject method is invoked.
        /// </summary>
        private static BusinessObjectConfiguration _BOC = null;

        /**//// <summary>
        /// Create a Business Object.
        /// </summary>
        /// <typeparam name="TInterface">An exposed Business Object Interface.</typeparam>
        /// <returns>Return Business Object instance that implementing TInterface.</returns>
        /// <exception cref="LiteMDA.BusinessObjectFactory.InterfaceNotExposedException">
        ///    Thrown when the specified TInterface is not in the exposed interface list.
        /// </exception>
        /// <exception cref="LiteMDA.BusinessObjectFactory.ConfigurationFileFormatErrorException">
        ///    Thrown when the the format of the configuration file for BO/BOI mapping is error.
        /// </exception>
        public static TInterface CreateObject<TInterface>()
        {
            if (_BOC == null)
            {
                // if this is the first time invoking CreateObject, load BOI/BO 
                // mapping pairs from the configuration file first.
                _BOC = ConfigurationManager.GetConfiguration("BusinessObjectConfiguration") as BusinessObjectConfiguration;
            }

            AssemblyClass ac = _BOC[typeof(TInterface).ToString()];

            if (ac != null)
            {
                //create object instance from the specified assemblyName and className
                Assembly ass = Assembly.LoadFile(AppDomain.CurrentDomain.BaseDirectory + ac.AssemblyName);
                if (ac.ClassName.Contains("`"))
                {
                    //It is a generic type, so fetch Type Parameters and bind then to the type before CreateInstance
                    Type t = ass.GetType(ac.ClassName.Substring(0, ac.ClassName.IndexOf("[")));
                    string typeParamListStr = ac.ClassName.Substring(ac.ClassName.IndexOf("[") + 1).TrimEnd(']');
                    string[] typeParamNames = typeParamListStr.Split(',');
                    Type[] typeParams = new Type[typeParamNames.Length];
                    for (int i = 0; i < typeParamNames.Length; i++)
                    {
                        typeParams[i] = Type.GetType(typeParamNames[i].Trim());
                    }
                    t = t.MakeGenericType(typeParams);
                    return (TInterface)Activator.CreateInstance(t);
                }
                else
                {
                    return (TInterface)ass.CreateInstance(ac.ClassName);
                }
            }
            else
            {
                throw new InterfaceNotExposedException(typeof(TInterface).ToString());
            }
        }
    }
}

几个测试类和接口代码如下：

ITestClass.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace LiteMDA.BusinessObjectFactory.Test
{
    public interface ITestClass
    {
        void TestMethod();
    }
}

ITestClass2.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace LiteMDA.BusinessObjectFactory.Test
{
    public interface ITestClass2
    {
        void TestMethod2();
    }
}

IGenericTestClass.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace LiteMDA.BusinessObjectFactory.Test
{
    public interface IGenericTestClass<T, U>
    {
        void TestMethod();
    }
}

TestClass.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace LiteMDA.BusinessObjectFactory.Test
{
    public class TestClass : ITestClass
    {
        ITestClass Members#region ITestClass Members

        public void TestMethod()
        {
            System.Windows.Forms.MessageBox.Show("OK");
        }

        #endregion
    }
}

GenericTestClass.cs

using System;
using System.Collections.Generic;
using System.Text;

namespace LiteMDA.BusinessObjectFactory.Test
{
    public class GenericTestClass<T, U> : IGenericTestClass<T, U>, ITestClass2
    {
        public void TestMethod()
        {
            System.Windows.Forms.MessageBox.Show("OK2");
        }

        public void TestMethod2()
        {
            System.Windows.Forms.MessageBox.Show("OK3");
        }
    }
}

测试代码如下：

        private void btnTestCreateBusinessObject_Click(object sender, EventArgs e)
        {
            ITestClass tc = ObjectFactory.CreateObject<ITestClass>();
            tc.TestMethod();
            IGenericTestClass<string, object> gtc = ObjectFactory.CreateObject<IGenericTestClass<string, object>>();
            gtc.TestMethod();
            ITestClass2 tc2 = ObjectFactory.CreateObject<ITestClass2>();
            tc2.TestMethod2();

        }

--
顺便说一下，以上的Configuration使用EnterpriseLibrary读写的。在vs.net 2005 beta2中使用EntLib我费了一番波折才搞定，这里说以下怎样设置，免得大家再走弯路。

你需要先用操作系统的搜索功能搜索entlib中src目录下所有包含"define VS2003"的.cs文件，大概十几个，把所有这些文件顶部的"VS2003"改成"VS2005B2"，然后用vs.net 2005 beta2（vc#2005beta2也一样）打开EnterpriseLibrary.sln重新编译所有程序集，同时请使用重新编后的Enterprise Library Configuration Tool来建立Application的App.config或web.config。

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